[Jukebox-list] Missing part of Wurlitzer 3700 Service Manual

[Gregor Anich]

Hmm...

In the manual they call it the "selection accumulator" - it is the thing below 
the record magazine with 200 latch pins which should be activated by the 
keyboard switches. There are 2 magnets inside which start rotating 
when "enough credits are in the box" (using the free-play switch) and when 
one if them is at the appropriate position it should get current from the 
keyboard switches and release the latch pin from the accumulator.

We put the gripper arm all the way down, and when we put the "load - scan - 
run" switch into the scan position and then switch the "service switch" (the 
one which says "technicians only" right to and in front of the record 
magazine) then the record magazine starts rotating. I don't know if this 
bypasses the override switch or not (would have to check ;)) but when i put 
my DMM onto the keyboard switches there is no voltage there which they could 
switch.

About the broken "C" switch - of course it will cause any switches after "C" 
not to work properly, but atm we are trying to get "A1" working.

-greg

On Wednesday 31 January 2007 05:10:26 Ron Rich wrote:
> Well,
>   First of all, it is my opinion that any switch contact cleaned with
> WD-40, and sandpaper of any grade probably will not make contact. The WD
> just coats it, and the sandpaper embeds into the silver causing poor
> contact to be made. This type of switch needs to be cleaned using a
> non-flammable solvent (sometimes referred to a "safety solvent") and
> finished with a burnishing tool. If "pitted", the pit must be removed with
> a file, followed by burnishing, and re-adjusting. The sliding switches
> (letters and numbers) can be cleaned by removing the whole keyboard assemb.
> removing the coil from the assemb. and washing the switch sections with
> sudsy ammonia, and a good rinsing with plain warm/ hot water--must be
> totally dry prior to use !! "Work" the switches while cleaning/rinsing. I
> think that after you do this, you will find that your readings are much
> improved. The overide contacts are prone to problems of not bing able to
> carry enough current to allow the basket motor to operate. A "digital
> meter", in most cases can not show this. They should be cleaned as above
> and tested with an "anolog" type meter. I don't recall an "override relay"
> controlling the motor--but maybe--see the schematic. If there is a relay,
> are it's internal contacts good--the basket should move (provided that the
> gripper arm has been put all the way down, over the basket, closing the
> "safety switch"), when the "override switch" is closed. You might check the
> operation of the solenoid that releases/powers the basket. There is a
> circuit breaker there that tends to trip, when the solenoid gets old
> (stuck). I do not under stand the # about the broken C switch--all switches
> must be good as it's a "ladder" type circuit, as you describe in the #
> above. What is the "accumulator"??
>   Ron Rich
>
>
> Gregor Anich <blight at blight.eu.org> wrote:
>   Hello!
>
> I checked the "I.D. Plate" - it is a 3700
>
> Yesterday and today I was at the place where the machine is and we were
> looking at the connections and switches...
>
> I do not understand what that override switch behind the basked is supposed
> to do, but when the machine is powered on and the override switch is moved,
> the override relay switches, so it seems to be ok?
>
> We cleaned all the "latch switches" on the keyboard because they didn't
> make good contact. We used some sandpaper (only a bit) and WD-40 to clean
> them, now they make good contact.
>
> There seems to be a problem with the letter switches on the keyboard.
> If none of the switches is pressed the "input signal" should flow from the
> first switch to the second to the third and so on, and when one switch is
> pressed it is disconnected from the following switches.
>
> But the "C" switch is broken (and maybe others) However I don't think that
> matters because there is nothing connected after the last switch "V" (to
> the contrary of the schematic)
>
> For the number switches there is something connected after the "0", but
> those kind of work - there are about 140 Ohms accross all number switches
> when none is pressed.
>
>
> Then we did the following to check all contacts between the keyboard and
> the accumulator:
> - put the accumulator into position "A1"
> - connect the DMM in diode/conduction testing mode to the chassis (GND) and
> signal 26 from the "TIMING BOARD" (lower right corner on Page 12F of the
> manual)
> - manually push the "latch arm" into the "latch solenoid" (like it was
> getting current) so the keyboard switches are latched and the "latch
> switches" are moved properly when a keyboard switch is pressed
> - press "A" and "1"
> - manually switch the "start relay" like it was getting current (to get
> signal 13 connected to GND)
>
> and we get a beep, with about 24 ohms resistance of which 23 come from the
> solenoid in the accumulator (which works if 12VDC are applied manually)
>
> So the connection from the control box to the keyboard through the latch
> switches and keyboard switches, down to the accumulator through the magnet
> and back up through the keyboard from which it finally goes back to the
> control box (signals 13 and 16) seems to be ok.
>
> Electronics are only my hobby so I am not really good at it.
> When looking at the timing board circuit I am not sure what it is supposed
> to do.
>
> The only possible path where enough current for the accumulator solenoid
> could come from seems through D6, signal 35.
> Signal 35 is connected to the rectifier D31-D34 and I guess it should
> be -28VDC?
>
> When I measure the voltage of signal 35 (before D6) on the timing board it
> says about 0VDC and 14VAC and 0VDC/AC after D6.
>
> Any ideas? :-)
>
> Thanks,
> greg